Toys should be fun to play with and look at, and stimulate creativity. Many toys achieve some but not all of those objectives. There are toy sets designed for small children that include a number of hard disks with radial slots that allow the pieces to be interfitted. Because the slots are radial and the pieces have limited flexibility, however, the shapes that can be made with such toy sets are linear and thus of limited interest.
There are also educational sets on the market that include hard plastic polygonal shapes that snap together along their edges to form polyhedra. Such sets are educational but do not have the play value and appearance of a toy product. Further, they require a relatively complex edge interfitting design.